Systems and Methods of Spatial Filtering for Measuring Electrical Signals

ABSTRACT

Disclosed herein are devices and methods of using a mobile or wearable device for the acquisition and spatial filtering of ECG signals from an electrode array. One variation of a mobile or wearable device comprises an array of electrodes, one or more reference electrodes, and a controller in communication with the electrodes. In one example, the one or more reference electrodes are located on a wrist-worn device (e.g., a watch), and the electrode array is located on an accessory device that may be contacted with a fingertip. One variation of a spatial filtering method comprises identifying the electrodes that have high levels of noise and excluding the ECG signals from those electrodes from further analyses. In another variation, a method of spatial filtering comprises identifying electrodes with low levels of noise and including only the ECG signals from those electrodes in further analyses.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/275,129, filed Sep. 23, 2016, which claims priority to U.S.Provisional Patent Application No. 62/235,362, filed Sep. 30, 2015, thecontents of which are hereby incorporated by reference in their entiretyas if fully disclosed herein.

FIELD

This relates generally to systems including a plurality of measurementelectrodes and methods for measuring one or more electrical signalsusing the plurality of measurement electrodes.

BACKGROUND

Electrocardiogram (ECG) waveforms can be generated based on theelectrical activity of the heart during each heartbeat. The waveformscan be recorded from multiple electrical leads attached to various areasof a patient's chest and limbs. FIG. 1 depicts one example of a 12-leadECG system 100 with a group of six measurement electrodes 102A, 102B,102C, 102D, 102E, and 102F that can be placed across the patient'schest, and four measurement electrodes 103A, 103B, 103C, and 103D thatcan be attached to the patient's limbs. The measurement electrodes forECG data acquisition can include a conducting or electrolytic gel (e.g.,Ag/AgCl gel) to provide a continuous, electrically-conductive pathbetween the skin and the electrodes. Such “wet” electrodes can reducethe impedance at the electrode-skin interface, thereby facilitating theacquisition of a low-noise ECG signal. All of the measurement electrodes102A, 102B, 102C, 102D, 102E, 102F, 103A, 103C, and 103D can beconnected to a control module 104, where signals from the measurementelectrodes can be transmitted to control module 104 for storage,processing, and/or displaying.

The signals from the ten measurement electrodes can be summed togetherto generate a single ECG waveform that can be viewed by the patientand/or a medical practitioner to evaluate the electrical activity of theheart. In some instances, the ECG signals from some of the measurementelectrodes can have larger fluctuations than the other measurementelectrodes. These larger fluctuations can be caused by noise due to, forexample, poor skin contact, other electronic devices and/or sources ofelectromagnetic radiation, and/or user motion artifacts. Since thesignals from the ten measurement electrodes can be summed together,discerning which among the ten measurement electrodes is associated withunsuitable levels of noise may be difficult. Reducing and/orcompensating for the effect of these noise sources may be desirable toyield an overall ECG waveform that has reduced noise levels andfacilitates interpretation by the patient and/or medical practitioner.

BRIEF SUMMARY

Disclosed herein are devices and methods of using a mobile or wearabledevice for the acquisition and spatial filtering of ECG signals from anelectrode array. The mobile or wearable device can comprise a pluralityof measurement electrodes, one or more reference electrodes, and acontroller in communication with the electrodes. In some examples, theelectrodes can be dry electrodes. In some variations, the one or morereference electrodes may be located on a wrist-worn device, such as abracelet, wrist band, or watch, such that the reference electrodes cancontact the skin in the wrist region, while the plurality of measurementelectrodes can be configured to contact a second, different skin region.In some examples, the plurality of measurements electrodes can belocated on a separate component from the reference electrode(s). In someexamples, some or all of the plurality of measurement electrodes can belocated on a wrist or finger cuff, a fingertip cover, a secondwrist-worn device, a region of the wrist-worn device that can bedifferent from the location of the reference electrode(s), and the like.One or more electrical signals measured by the plurality of measurementelectrodes can be spatially filtered by the controller such each signalcan be capable of being individually rejected if the signal has morenoise relative to the signals from other measurement electrodes. Forexample, the controller of the mobile or wearable device can employvarious methods to determine which measurement electrode(s) have noiselevels that exceed a predetermined and/or computed noise threshold andcan exclude the input from those measurement electrode(s) in thecomputation of the ECG waveform. The noise threshold may, for example,be the average noise level from all of the plurality of measurementelectrodes as computed by the controller. In some examples, signals fromthe measurement electrode(s) with suprathreshold levels (i.e., signallevels greater than a second predetermined threshold) of noise can beincorporated into the ECG waveform, but can be given less weight lessthan signals from measurement electrode(s) with subthreshold levels ofnoise (i.e., signal levels less than a first predetermined threshold,where the first predetermined threshold can be less than the secondpredetermined threshold).

In some examples, the plurality of measurement electrodes can beconnected to the controller via an interface module. The interfacemodule can include one or more multiplexers having a plurality ofselectable channels connected to each of the plurality of measurementelectrodes. In some examples, each measurement electrode can have adedicated channel in the multiplexer; in other examples, the measurementelectrodes can share a channel with one or more other measurementelectrodes such that the multiplexer can selectively connect themeasurement electrodes to the controller based on commands from thecontroller. The connections between the measurement electrodes and theinterface module can be wired or wireless, and/or the connectionsbetween the interface module and the controller may be wired orwireless. Examples of wireless communication protocols can includeWi-Fi, Bluetooth, near field communication (NFC), cellular, and/or otherwireless communication techniques. The controller can issue commands tothe interface module such that connections to measurement electrodeswith subthreshold levels of noise (i.e., “low-noise” measurementelectrodes) can be preferred or prioritized over the connections tomeasurement electrodes with suprathreshold levels of noise (i.e.,“high-noise” measurement electrodes). For example, low-noise measurementelectrodes can be sampled more frequently than high-noise measurementelectrodes, and in some variations, high-noise measurement electrodesmay not be sampled at all. In instances where multiple measurementelectrodes can share a single channel on a multiplexer of the interfacemodule, fewer wires (e.g., leads) may be used and the size of thewearable or mobile device upon which some or all of the measurementelectrodes is mounted can be smaller. Regulating the multiplexerconnections such that low-noise measurement electrodes are favored overhigh-noise measurement electrodes can allow for this reduction inhardware size and complexity with little or no impact on the sampling oflow-noise measurement electrodes.

Also described herein are methods of spatially filtering signals.Spatial filtering methods can comprise identifying measurementelectrodes with subthreshold levels of noise (e.g. by comparing thenoise from each measurement electrode with a noise threshold),optionally identifying measurement electrodes with suprathreshold levelsof noise, and analyzing the signals from the measurement electrodes withsubthreshold levels of noise. For example, some methods may comprisegenerating an overall ECG waveform and/or computing the user's heartrate based primarily on ECG data from measurement electrodes withsubthreshold levels of noise. In some examples, spatial filtering cancomprise eliminating or not acquiring ECG data from measurementelectrodes with suprathreshold levels of noise (e.g., only acquiring ECGdata from measurement electrodes with subthreshold levels of noise). Insome examples, spatial filtering can comprise adjusting the samplingrate or frequency of high-noise measurement electrodes to be less thanthe sampling rate or frequency of low-noise measurement electrodes.Optionally, the controller can increase the sampling frequency on themeasurement electrodes with subthreshold noise levels. Alternatively oradditionally, spatial filtering methods may comprise scaling down thecontribution of the high-noise measurement electrodes when computing theoverall ECG waveform and/or computing the user's heart rate. In someexamples, the measurement electrodes that have the least amount of noisecan have a dedicated channel through the interface module so that thecontroller can receive measurements from that measurement electrode atthe highest sampling frequency, while the measurement electrodes thathave suprathreshold noise levels may share a channel with othermeasurement electrodes having relatively high levels of noise, such thatthe effective sampling frequency of these high-noise electrodes can bereduced. In doing so, for a given data acquisition interval, thecontroller can acquire more data from low-noise measurement electrodesand less data from the high-noise measurement electrodes. In somevariations, the ECG waveform can be more heavily weighted towards ECGdata measured by the low-noise measurement electrodes, while stillrepresenting ECG data (albeit at a lower weight or degree) from thehigh-noise measurement electrodes.

Described herein is an exemplary wearable electrocardiographic (ECG)device that can comprise a plurality of dry measurement electrodes,which can be measurement electrodes configured to contact a skin surfaceand capable of obtaining an accurate signal without the use of aconducting or electrolytic gel. The plurality of dry measurementelectrodes can be in communication with a controller, which can beconfigured to receive signals from the plurality of measurementelectrodes at a first sampling frequency. In some examples, thecontroller can be configured to generate an ECG waveform using theaverage of the signals from the plurality of measurement electrodes thatdo not exceed the noise threshold. The ECG waveform may be, for example,a weighted sum of the signals from the plurality of measurementelectrodes, where the weighting factor for the each signal can beinversely proportional to the noise level of that measurement electrode.For example, the weighting factor for signals from measurementelectrodes with suprathreshold noise levels may be zero. The weightingfactor can vary as a function of time in some examples. Optionally, thewearable ECG device can comprise a display in communication with thecontroller, where the controller can be configured to output the ECGwaveform to the display for viewing. In some examples, the controllercan be configured to transmit the ECG signals to a companion device. Thecompanion device can comprise a controller that can be configured tocombine the signals from measurement electrodes that have noise levelsthat do not exceed the noise threshold to generate an ECG waveform. Thecompanion device controller can be configured to generate an ECGwaveform by averaging the ECG signals from measurement electrodes thathave noise levels that do not exceed the noise threshold. In somevariations, the controller can be configured to compute one or morephysiological parameters (e.g., a heart rate) of the user based on theECG waveform.

In some variations, the array of dry electrodes may be located on awrist-worn device, and/or may be configured to communicate wirelessly tothe controller. The noise threshold may be predetermined or computed.For example, the noise threshold may be derived from the average noiselevel of all of the signals, and the controller may be configured tocompare the noise levels from each of the measurement electrodes withthis computed noise threshold to identify the measurement electrodesthat have suprathreshold noise levels. The controller may be configuredto compare the noise levels of the measurement electrodes at a selectedfrequency, where the selected frequency may be the sampling frequency.The controller may be configured to identify and reject the data fromany measurement electrode that has a noise level that can be more thanone standard deviation from the noise threshold. For example, thecontroller may be configured to identify and reject the data from anymeasurement electrode that has a noise level that can be more than twostandard deviations from the noise threshold. The controller may beconfigured to sample each measurement electrode at a selected samplingfrequency, wherein the sampling frequency can be inversely related tothe noise level of that measurement electrode. In some examples, thesampling frequency for a measurement electrode with noise levels greaterthan two standard deviations from the noise threshold can be zero.

Some examples can include an ECG device further comprising an interfacemodule including a multiplexer in communication with the plurality ofmeasurement electrodes and the controller. The multiplexer may beconfigured to dynamically connect the controller to electrodes that havethreshold or subthreshold levels of noise. In some examples, themultiplexer may be configured to provide a connection between thecontroller and the measurement electrode(s) that have threshold orsubthreshold noise levels such that these measurement electrodes can besampled by the controller at a second sampling frequency (e.g., thesecond sampling frequency may be the same as the first samplingfrequency). The multiplexer may, in some variations, be configured toprovide a connection between the controller and the measurementelectrode(s) that have suprathreshold noise levels such that thesemeasurement electrodes can be sampled by the controller at a thirdsampling frequency, which can be less than the second samplingfrequency.

Also described herein are methods of spatial filtering. For example, amethod for spatial filtering across a plurality of measurementelectrodes can comprise contacting a reference electrode to a first skinregion on a user, contacting one or more of the plurality of measurementelectrodes to a second skin region on the user, where the referenceelectrode and the plurality of measurement electrodes can be incommunication with a controller, measuring noise levels for eachmeasurement electrode, computing a noise threshold based on an averagenoise level across all of the measurement electrodes, and acquiringsignals from the measurement electrodes that have noise levels at orbelow the noise threshold. In some examples, the method may furthercomprise averaging the acquired signals, using the controller, togenerate an ECG waveform. Optionally, some methods may further compriseacquiring signals from the measurement electrode(s) that have noiselevels above the average noise level. The signals from high-noisemeasurement electrodes with suprathreshold noise levels may be acquiredat a lower sampling frequency than the signals from measurementelectrodes with threshold or subthreshold noise levels. Measuring noiselevels may comprise measuring the impedance of each measurementelectrode. In some examples, the method may also comprise comparing theaverage noise level to a predetermined noise threshold, and if thecontroller determines that the average noise level exceeds thethreshold, generating a notification to the user to position one or moreof the plurality of measurement electrodes at a different skin locationand/or apply pressure to the measurement electrode(s). Optionally, themethod may further comprise displaying the ECG waveform to the user. Insome variations, the communication between the plurality of measurementelectrodes and controller may be modulated by a multiplexer. Themultiplexer may connect the controller more frequently to measurementelectrodes that have threshold or subthreshold noise levels and lessfrequently to measurement electrodes that have suprathreshold noiselevels.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematic depiction of a traditional ECG system.

FIG. 2A illustrates a personal electronic device in accordance with someexamples.

FIG. 2B is a block diagram illustrating a personal electronic device inaccordance with some examples.

FIG. 3A is a perspective view of one variation of a watch that may beused for the acquisition and processing of signals from the measurementand/or reference electrodes.

FIG. 3B is view of the back of the watch of FIG. 3A.

FIG. 3C is another variation of the back of the watch of FIG. 3A.

FIG. 3D depicts the skin contours of a finger.

FIG. 4A is a schematic of one variation of a system for the acquisitionand spatial filtering of signals.

FIG. 4B depicts a circuit schematic that represents one variation of aninterface module.

FIG. 4C depicts a circuit schematic that represents another variation ofan interface module.

FIG. 4D depicts one example of the plurality of measurement electrodesand associated traces.

FIG. 4E illustrates example signals measured from eight measurementelectrodes and an overall ECG waveform derived from the signals withsubthreshold noise levels.

FIG. 5A is a flowchart that depicts a variation of a spatial filteringmethod.

FIG. 5B is a flowchart that depicts a variation of a spatial filteringmethod.

DETAILED DESCRIPTION

Disclosed herein are devices and methods of using a mobile or wearabledevice for the acquisition and spatial filtering of signals from aplurality of measurement electrodes. The mobile or wearable device maycomprise a plurality of measurement electrodes, one or more referenceelectrodes, and a controller in communication with the measurementand/or reference electrodes. In some examples, the measurementelectrodes can be dry electrodes. In some examples, the mobile orwearable device may comprise an interface module in communication withthe measurement electrodes and the controller, where the interfacemodule can be configured to adjust the connectivity between theplurality of measurement electrodes and the controller. In someexamples, the interface module may comprise one or more multiplexersconfigured for the selection of individual and/or sets of measurementelectrodes based on command signals from the controller. Methods ofspatial filtering the signals from the measurement electrodes maycomprise using the interface module to selectively transmit data fromlow-noise measurement electrode(s). Data from the measurementelectrode(s) that have been determined to have high levels of noise(e.g., noise levels that exceed a predetermined and/or computed noisethreshold) may be filtered out and may not be included in the generationof the overall ECG waveform. In some examples, filtering out data fromhigh-noise measurement electrodes may comprise adjusting theconnectivity of the multiplexer(s) of the interface module such thatdata from these high-noise measurement electrodes may not transmitted tothe controller. Alternatively or additionally, filtering out data fromhigh-noise measurement electrodes may comprise adjusting theconnectivity of the multiplexer such that the frequency or rate at whichthe multiplexer connects the controller to the high-noise measurementelectrodes can be lower than the frequency or rate at which themultiplexer(s) connect the controller to the low-noise measurementelectrodes. In examples where each of the measurement electrodes has adedicated channel to the controller, spatial filtering the signalsacross the plurality of measurement electrodes may comprise thecontroller rejecting, ignoring, and/or eliminating the data from thehigh-noise measurement electrodes from data analysis and interpretation.For example, the controller may incorporate only the signals fromlow-noise measurement electrodes in the computation of the overall ECGwaveform. In some variations, the controller may generate an overall ECGwaveform by computing a weighted sum across all of the measurementelectrode signals. Spatial filtering of the signals from the pluralityof measurement electrodes may comprise assigning a weight to aparticular measurement electrode signal that can be inversely related(e.g., inversely proportional, etc.) to its ranked noise level ascompared to the other measurement electrodes and/or the average noiselevel across all of the electrodes. In this variation, the signal(s)from high-noise measurement electrode(s) may be incorporated in theoverall ECG waveform, but at a relatively lower weight as compared tothe signal(s) from low-noise measurement electrode(s). Reducing thecontribution of high-noise measurement electrode(s) may also reducetheir impact to the signal-to-noise ratio (SNR) of the overall ECGwaveform.

Although the examples and applications of spatial filtering devices andmethods are described in the context of generating a complete ECGwaveform, it should be understood that the same or similar devices andmethods may be used to collect and process data from the plurality ofmeasurement electrodes and may or may not generate an ECG waveform. Forexample, the spatial filtering of the signals from the plurality ofmeasurement electrodes may facilitate the monitoring of certain cardiaccharacteristics (e.g., heart rate, arrhythmias, changes due tomedications or surgery, function of pacemakers, heart size, etc.) and/orECG waveform characteristics (e.g., timing of certain waves, intervals,complexes of the ECG waveform) by the controller and/or user withoutgenerating a complete ECG waveform. In some examples, the controller maygenerate a subset of the ECG waveform (e.g., one or more of the P wave,QRS complex, PR interval, T wave, U wave) based on spatially filteredmeasurement electrode signals. The ECG devices described herein mayoptionally comprise a display that can provide a visual representationof the collected and/or filtered measurement electrode data to the user.Alternatively or additionally, the filtered measurement electrode datamay not be displayed by the ECG device, but instead can be relayed to acompanion device (e.g., a tablet, laptop, smartphone, computer, server,etc.) that can have a display for outputting a visual representation ofthe data. Moreover, examples of the disclosure include spatial filteringdevices and methods configured for other types of measurementsincluding, but not limited to, EEG and EMG measurements or opticaldetermination of parameters on blood constituents.

The terminology used in the description of the variations describedherein is for the purpose of describing particular variations only andis not intended to be limiting. As used in the description of thevarious described variations and the appended claims, the singular forms“a”, “an,” and “the” are intended to include the plural forms as well,unless the context clearly indicates otherwise. It will also beunderstood that the term “and/or” as used herein refers to andencompasses any and all possible combinations of one or more of theassociated listed items. It will be further understood that the terms“includes,” “including,” “comprises,” and/or “comprising,” when used inthis specification, specify the presence of stated features, integers,steps, operations, elements, and/or components, but do not preclude thepresence or addition of one or more other features, integers, steps,operations, elements, components, and/or groups thereof.

The term “if” may be construed to mean “when” or “upon” or “in responseto determining” or “in response to detecting,” depending on the context.Similarly, the phrase “if it is determined” or “if [a stated conditionor event] is detected” may be construed to mean “upon determining” or“in response to determining” or “upon detecting [the stated condition orevent]” or “in response to detecting [the stated condition or event],”depending on the context.

Variations of electronic devices, user interfaces for such devices, andassociated processes for using such devices are described. In somevariations, the device can be a portable communications device, such asan internet-enabled telephone such as a smartphone, a mobile telephone,or a wearable communications device, such as a wristband, watch, clip,headband, earphone or ear piece, internet-enabled eyewear, or anycomputing device, portable or otherwise, such as a personal calendaringdevice, electronic reader, tablet, desktop, or laptop computers, etc.Any of these devices may also include other functions, such as personaldigital assistant (PDA) and/or music player functions. Optionally, anyof the above-listed electronic devices may comprise touch-sensitivesurfaces (e.g., touch screen displays and/or touchpads). Alternativelyor additionally, the electronic devices may include one or more otherphysical user-interface devices, such as a physical mouse, a keyboard,and/or a joystick.

FIG. 2A illustrates exemplary personal electronic device 200, such asone that may be used for acquiring and spatially filtering signals fromelectrode arrays for generating ECG waveforms. Device 200 includes body202. Personal electronic device 200 may be a portable device such as atablet, smart phone, watch, and in some variations, may be part of awireless-capable eyepiece or eye-wear, head gear, and the like. In othervariations, personal electronic device 200 may not be a portable device,and may be desktop computer. In some variations, device 200 hastouch-sensitive display screen 204. Alternatively, or in addition totouch screen 204, device 200 may have a display and a touch-sensitivesurface. In some variations, touch screen 204 (or the touch-sensitivesurface) may have one or more intensity (force) sensors for detectingintensity of contacts (e.g., touches) being applied. The one or moreintensity sensors of touch screen 204 may provide output data thatrepresents the intensity of touches. The user interface of device 200can respond to touches based on their intensity. For example, touches ofdifferent intensities can invoke different user interface operations ondevice 200.

FIG. 2B depicts the various components of exemplary personal electronicdevice 200. Similar components may also be included in any of thedevices described herein (e.g., device 300, 310 of FIGS. 3A-3C). Device200 can include a bus 212 that operatively couples I/O section 214 withone or more computer processors 216 and memory 218. I/O section 214 maybe connected to display 204, which may have a touch-sensitive component222 and, optionally, a touch-intensity sensitive component 224. Inaddition, I/O section 214 may be connected with communication unit 230for receiving application and operating system data, using Bluetooth,Wi-Fi, near field communication (NFC), cellular, and/or other wirelesscommunication techniques. Device 200 may include input mechanisms 206and/or 208. Input mechanism 206 may be a rotatable input device or adepressible and rotatable input device, for example. In some examples,input mechanism 208 may be a button.

Input mechanism 208 may be a microphone, in some examples. Personalelectronic device 200 can include various sensors, such as GPS sensor232, accelerometer 234, directional sensor 240 (e.g., compass),gyroscope 236, motion sensor 238, and/or a combination thereof, all ofwhich can be operatively connected to I/O section 214. Examples with ECGmeasurement capabilities, described in greater detail below, may includeone or more reference electrodes 242 and an array of measurementelectrodes 244. The connection between the various sensors and the I/Osection 214 may be an electrical wire or bus, and/or wireless (e.g.,Bluetooth, Wi-Fi, near field communication (NFC), cellular, and/or otherwireless communication techniques).

Memory 218 of personal electronic device 200 can be a non-transitorycomputer-readable storage medium, for storing computer-executableinstructions, which, when executed by one or more computer processors216, for example, can cause the computer processors to perform thetechniques and methods described herein. The computer-executableinstructions can also be stored and/or transported within anynon-transitory computer-readable storage medium for use by or inconnection with an instruction execution system, apparatus, or device,such as a computer-based system, processor-containing system, or othersystem that can fetch the instructions from the instruction executionsystem, apparatus, or device and execute the instructions. A“non-transitory computer-readable storage medium” can be any medium thatcan tangibly contain or store computer-executable instructions for useby or in connection with the instruction execution system, apparatus, ordevice. The non-transitory computer-readable storage medium can include,but is not limited to, magnetic, optical, and/or semiconductor storages.Examples of such storage include magnetic disks, optical discs based onDVD, CD, or Blu-ray technologies, as well as persistent solid-statememory such as flash, solid-state drives, and the like. Personalelectronic device 200 may not be limited to the components andconfiguration of FIG. 2B, but can include other or additional componentsin multiple configurations. As described herein, a “controller” mayrefer to a system comprising a computer processor such as amicroprocessor, central processing unit (CPU), a digital signalprocessor (DSP), programmable logic device (PLD), and/or the like.

In some variations, device 200 may have one or more input mechanisms 206and 208. Input mechanisms 206 and 208, if included, can be physical.Examples of physical input mechanisms may include rotatable mechanismsand push buttons. In some variations, device 200 may have one or moreattachment mechanisms. Such attachment mechanisms, if included, canpermit attachment of device 200 with, for example, hats, eyewear,earrings, necklaces, shirts, jackets, pockets, collars, bracelets, watchstraps, chains, trousers, belts, shoes, socks, purses, backpacks,undergarments, and so forth. These attachment mechanisms may permitdevice 200 to be worn by a user.

Attention is now turned toward variations of additional device modulesand associated processes that may be implemented on an electronicdevice, such as portable multifunction device 300, for acquiring ECGsignals from an electrode array and spatial filtering of those signals.

FIGS. 3A-3C depict one variation of a mobile or wearable device 300 thatmay be used to acquire and spatially filter signals from a plurality ofmeasurement electrodes. The device 300 may be a wrist-worn device, suchas a watch, bracelet, or wrist band. The device 300 may comprise one ormore reference electrodes 302 located on a skin-contacting surface ofthe device. For example, the device may be a watch having a housing witha front side 306 that can face the user and a back side 308 that cancontact the skin region around the wrist. As depicted in FIG. 3B, areference electrode 302 can be located on the back side 308. In thisexample, only one reference electrode 302 is depicted, however, in othervariations, such as depicted in FIG. 3C, there may be more than onereference electrode (e.g., 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 14, 15 ormore, etc.).

In some examples, a plurality of measurement electrodes 310 may belocated on the device 300 (e.g., on the back side 308 and/or front side306), as illustrated in FIG. 3A. In some examples, the plurality ofmeasurement electrodes can be located on an accessory that can beseparate or detached or detachable from the device 300. One or more ofthe plurality of measurement electrodes can be provided at variouslocations or regions of the device 300. For example, plurality ofmeasurement electrodes 310 can be located at a first side wall portionR1 of the device 300 and/or a second side wall portion R3 of the device.Alternatively or additionally, one or more measurement electrodes can belocated on the outward-facing surface of the wrist band of the device300. For example, one or more measurement electrodes can be on theoutward-facing surface of the band R2 located below the housing or canbe on the outward-facing surface of the band located above the housingR4. Some examples may include a first one or more measurement electrodeslocated at R1 and a second one or more measurement electrodes located atR2. The user's ECG data can be collected when the user puts his/herthumb on the first one or more measurement electrodes and his/her indexfinger on the second one or more measurement electrodes. In someexamples, there may only be one location included measurement electrodeson the device 300. The signals measured by the one or more measurementelectrodes can be transmitted to the device 300 using wirelesscommunications or using one or more electrical wires or cables.

The electrodes of the electrode arrays described herein may be “dry”electrodes. “Dry electrodes” can be electrodes configured to contact theuser without use of a conducting or electrolytic gel located between theuser's skin and any surface of the electrodes. Typically, ECGmeasurement systems use wet Ag/AgCL electrodes. Without the aid of suchgels, obtaining electrical signals with an acceptable or favorable SNRcan be challenging. Low-frequency noise (e.g., about 0.5 Hz to about 40Hz) may be introduced at the electrode-skin interface. This frequencyband also encompasses the ECG signals-of-interest, which may pose achallenge (e.g., make it computationally intensive) to filtering out thenoise without diminishing the signal strength and/or integrity. Withoutwishing to be bound by theory, sources of such low-frequency noise mayinclude sweat glands (e.g., due to electrolyte behavior), local motionartifacts, local dead skin and other skin irregularities, as well asnon-homogenous skin contact. Furthermore, measuring ECG signals fromdifferent sites on the limbs (e.g., hand(s), finger(s), feet, toe(s))may introduce noise of a highly stochastic nature. Such stochastic noisemay have a peak-peak value great than about 50 μVpp, which can exceedthe noise threshold that can be acceptable for ECG measurements andwaveforms. In some cases, these noise sources may be localized andspatially specific. That is, if an electrode array is placed on a smallpatch of skin (e.g., about 1 cm², about 2 cm², etc.), the measurementsfrom one electrode in the electrode array can be affected by noise fromsweat glands, while another electrode in the electrode array may not beaffected by sweat glands. In this example, the distribution of noiseacross the electrode array can depend on the distribution of sweatglands across that patch of skin.

In some instances, the electrode array can make poor or inconsistentcontact with the user's skin. This may be particularly the case when ECGdata is being collected from anatomical structures with irregular curvesand shapes, such as from a fingertip. FIG. 3D schematically depicts afinger, which may have a constantly-changing surface (denoted by theconstantly-changing slopes of the dotted lines), as well as concave orconvex regions (a concave region is enclosed in the dotted oval). Othergeometric surface irregularities may also include curves that havenon-constant radius of curvature, skin folds or clefts, variable surfaceelasticity of different types of tissue (e.g., finger nails, bones, arerelatively inelastic as compared to skin), etc. These irregularities mayincrease the impedance of an electrode and render the ECG signalsacquired by that electrode particularly susceptible to noise (especiallyfrom motion artifacts).

The devices and methods disclosed herein address these and other sourcesof noise by utilizing a plurality ofindividually-controllable/measurable measurement electrodes and spatialfiltering of the signals acquired by the plurality of measurementelectrodes. Spatial filtering of the signals acquired by the pluralityof measurement electrodes may comprise measuring the noise levels foreach of the measurement electrodes, determining which measurementelectrode(s) have noise levels that are at, above, or below a noisethreshold, and excluding the data from high-noise measurementelectrode(s) in the computation of the overall ECG waveform. Filteringout the signals from the high-noise measurement electrode(s) may improvethe quality of the overall ECG waveform and/or simplify thecomputational processing of the ECG data acquired by the measurementelectrodes.

FIG. 4A depicts a schematic functional block diagram of an exemplarysystem for measuring ECG signals from a plurality ofindividually-controllable/measurable measurement electrodes and spatialfiltering those signals. The system 400 may comprise plurality ofmeasurement electrodes 402, a controller 404, and an interface module406. Interface module 405 can be configured to transmit signals from theplurality of measurable electrodes 402 to the controller 404. One ormore reference electrodes may be in communication with the interfacemodule and/or controller. The communication channel 403 (between theplurality of measurement electrodes 402 and the interface module 406)and the communication channel 405 (between the interface module 406 andthe controller 404) may be wired or wireless. The communication channelsmay transmit signals that can represent measured ECG data or signals,controller commands to the interface module, and the like. In someexamples, the signal transmitted to the controller can be a differentialsignal (e.g., a signal representing the difference between signal valuesmeasured at two or more measurement electrodes). As described previouslywith regard to FIGS. 3A-3C, the plurality of measurement electrodes 402,interface module 406, and the controller 404 may be located on the samedevice or may be located on separate devices or components. For example,the plurality of measurement electrodes 402, interface module 406, andthe controller 404 may all be located on a wrist-worn device such as awatch. Alternatively, the interface module 406 and the controller 404may be located on the wrist-worn device while the plurality ofmeasurement electrodes 402 may be located on a separate accessorydevice. In some examples, the communication channel 403 may be wireless,while the communication channel 405 may be wired. In some examples, theelectrode array 402 and the interface module 406 may be located on anaccessory device, and the controller may be located on a wrist-worndevice. In some examples, the communication channel 403 may be wired,while the communication channel 405 may be wireless. Although theplurality of measurement electrodes 402 is depicted as having fourelectrodes in FIG. 4A, it should be understood that the plurality ofmeasurement electrodes may comprise any number of electrodes, as may bedesirable. For example, the plurality of measurement electrodes 402 maycomprise 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 15, 20, 22, 24, 25, 27, 30,etc. electrodes. The arrangement of these measurement electrodes mayvary, for example, depending on the size and size of the anatomicalregion from which the plurality of measurement electrodes can be used tomeasure ECG signals. For example, the plurality of measurementelectrodes may be arranged as a circle, rectangle, diamond, triangle, ina line, or in any anatomically-specific fashion, etc.

The interface module 406 can be configured to amplify and filter thesignals from the electrodes. In some examples, the interface module 406can selectively transmit the signals measured by the plurality ofmeasurement electrodes to the controller. For example, the interfacemodule 406 may comprise one or more buffers, filters (e.g., 60 Hz notchfilters, bandpass filters, etc.), amplifiers (e.g., differentialamplifiers, etc.), and/or analog-to-digital converter (ADC). In someexamples, the raw signals measured by the plurality of measurementelectrodes may be filtered, amplified, and converted to a digital signalbefore the signals are transmitted from the interface module to thecontroller. Optionally, in some variations, the interface module 406 maycomprise a switch circuit, such as a multiplexer, where ECG signals fromeach of the measurement electrodes can be transmitted to the multiplexer(either before or after amplifying, filtering and/or converting to adigital signal). Based on commands from the controller, the multiplexercan selectively output or transmit the data from certain measurementelectrodes to the controller. The number of multiplexer output channelsmay be the same as or less than the number of measurement electrodes.Multiplexing the data collected by the plurality of measurementelectrodes may help to reduce the number of signal processing componentsin the interface module, thereby reducing the size of the overalldevice. In some examples, the interface module may comprise a pluralityof multiplexers, for example, arranged serially or in stages.Furthermore, the multiplexer may be used to selectively transmit thesignals from the relatively low-noise measurement electrodes to thecontroller instead of the signals from the relatively high-noisemeasurement electrodes. By doing so, the multiplexer can spatiallyfilter the signals from the measurement electrodes based on commandsfrom the controller by rejecting the high-noise signals and transmittingthe low-noise signals.

FIGS. 4B-4C depict examples of interface modules 416, 426 that comprisea plurality of amplifiers and multiplexers. FIG. 4B depicts an interfacemodule 416 that comprises amplifiers 410 and multiplexers 412, such thatthe signals from each measurement electrode 402 can be amplified beforethey arrive at the input ports of the multiplexers. In some examples,interface module 416 can include circuitry configured to reject anysignals from measurement electrodes 402 that may be associated with highnoise (i.e., the noise is greater than a noise threshold). In thismanner, only low-noise signals can be transmitted through communicationchannel 405 to controller 404. In some examples, the high-noise signalsmay be rejected (e.g., not sent through communications channel 405 tocontroller 404) for a certain time period, followed by a periodiccheck/determination whether the electrodes associated with thepreviously high-noise signals are now associated with low-noise signals.Although the multiplexers 412 are depicted as having two input ports, itshould be understood that multiplexers might have any number of inputports as may be desirable.

In some examples, interface module 416 can include circuitry that maynot entirely reject signals associated with high noise, but instead maysample (and transmit to controller 404) the signals associated with highnoise at a different frequency (e.g., lower frequency) than the signalsassociated with low noise. In some examples, interface module 416 caninclude circuitry that may weigh the signals associated with high noisedifferently than the signals associated with low noise. For example, thehigh-noise signals can be given a lower weight (i.e., relativecontribution to the overall ECG signal) than low-noise signals.

FIG. 4C depicts another variation of an interface module 426 thatcomprises amplifiers 420 and multiplexers 422, such that the signalsfrom each measurement electrode 402 can be selected by the multiplexerbefore they are amplified. In still other variations, differentialamplifiers may be used (in either the circuit topology of FIG. 4B orFIG. 4C), where the first input to a differential amplifier may be ameasurement electrode, and the second input to the differentialamplifier may be a reference electrode (and/or an electrode selectedfrom a plurality of reference electrodes). In some examples, the inputsignals (e.g., from the plurality of measurement electrodes and areference electrode or reference electrode array) to one or moredifferential amplifiers may be pre-selected by one or more multiplexersso that the low-noise ECG signals can be amplified and processed.

In some examples, the interface module 426 can be configured to grouptogether (e.g., via one or more switches) low-noise signals and can beconfigured to group together high-noise signals. The group of low-noisesignals can be measured at one frequency, and the group of high-noisesignals can be measured at another frequency. For example, the group oflow-noise signals can be measured more frequently than the group ofhigh-noise signals.

FIG. 4D depicts an exemplary plurality of measurement electrodes andassociated spatial filtering of the measurement electrodes outputs.Plurality of measurement electrodes 420 comprises nineindividually-addressable/controllable measurement electrodes 421-429that can be arranged in a square (diamond) shape. In other examples, anynumber of measurement electrodes can be arranged in any shape. Eachtrace can be coupled to a unique electrode (e.g., electrode 421, 422,423, 424, 426, 427, 428, 429, respectively (the trace coupled toelectrode 425 is not depicted)), and separate signals 431, 432, 433,434, 436, 437, 438, 439 can be measured and transmitted to thecontroller. Signals from the traces can be acquired during a portion ofthe cardiac cycle with minimal cardiac activity, such as the inter-beatinterval. The controller can determine that the peak value or magnitudeof the signals 437-430 from electrodes 427-429 can be higher than thepeak value or magnitude of the signals from the other electrodes, andsuch fluctuations can be the result of noise.

In some examples, the controller can average all of the signals 431-439to obtain an average signal that can represent a noise threshold againstwhich the signals from the measurement electrodes can be compared. Forexample, the controller may compute the peak value or magnitude of thataverage signal, and compare the peak value or magnitude of each of thesignals 431-439 with that of the average signal to identify measurementelectrodes that have suprathreshold values or magnitudes. Suchmeasurement electrodes can be considered as “high-noise” measurementelectrodes. These high-noise electrodes may be determined to be locatedat or contacting skin regions that give rise to higher levels of noise,for example. For example, without wishing to be bound by theory, thenoise that affects the electrodes 427-429 (which may be located in acontiguous spatial region) may arise from sweat glands that can beco-located with the electrodes 427-429. In some instances, the skinregion that contacts electrodes 421-426 may have fewer, if any, sweatglands than the skin region contacted by electrodes 427-429. Once thecontroller has identified electrodes 427-429 as high-noise electrodes,the signals from the high-noise electrodes may be excluded fromgenerating the overall ECG waveform. For example, electrodes 427-429 canbe grouped together, and electrodes 421-426 can be grouped together.Signal 430 can represent the sum of the signals 431-436 associated withlow-noise measurement electrodes; signals 437-439 from high-noisemeasurement electrodes can be excluded. The signals from electrodes427-429 may be excluded by adjusting the channel selection of themultiplexer(s) in the interface module such that signals from high-noisemeasurement electrodes may not selected for transmission to thecontroller. In this manner, more bandwidth can be made available betweenthe interface module and the control module for the transmission ofsignals from low-noise measurement electrodes 421-426. In some examples,the signals from high-noise measurement electrodes 427-429 may betransmitted to the controller (along with the signals from the low-noisemeasurements electrodes 421-426), but not included in the determinationof the overall ECG waveform.

The device can operate with any configuration for sampling ECG data. Forexample, all measurement electrodes (e.g., measurement electrodes421-429) can sample ECG data at the same time, and the signals can betransmitted to the controller at the same time. In some examples, themeasurement electrodes can sample ECG data sequentially (e.g., electrode421 can sample ECG data first, followed by electrode 422 sampling datasecond, etc.), and the signals can be transmitted to the controllersequentially. In some examples, the device can perform an initial scanincluding sampling all of the measurement electrodes to determinewhether one or more measurement electrodes include suprathreshold noiselevels. Subsequent scans can exclude the measurement electrodes withsuprathreshold noise levels, but can include the electrodes withsubthreshold noise levels.

In some examples, the device can simultaneously sample ECG data frommultiple electrodes to further reject or disable electrodes. Forexample, electrode 421 and electrode 429 can simultaneously sample ECGdata. If the noise levels from the measurements differ, then the devicecan determine whether to use the measurements from the measurementelectrode with lower noise levels or disable the measurement electrodewith higher noise levels.

In some examples, each of the measurement electrodes can be coupled to aunique communication channel. FIG. 4E depicts an example of spatialfiltering of ECG data from eight measurement electrodes (electrodesrepresented by channels 1-8). The signals 440 from the eight measurementelectrodes can have varying degrees of noise, with the signal 442 fromchannel 8 having the greatest amount of noise. The signal 442 fromchannel 8 may be identified as having suprathreshold noise levels by thecontroller and can be filtered out (e.g., excluded from the computationof the overall ECG waveform). Signal 444 can be the overall ECG waveformgenerated by the data from channels 1-7, and can exclude data fromchannel 8. Spatial filtering the signals from the eight measurementelectrodes to exclude data from channel 8 may help to preserve theintegrity of the overall ECG waveform, and limit (or entirely eliminate)the effect of electrodes with suprathreshold noise levels on the ECGwaveform.

FIGS. 5A-5B are flowchart depictions of variations of methods of spatialfiltering that may be performed by a controller of a mobile or wearabledevice for acquiring ECG signals. Some methods of spatial filtering maycompletely eliminate or reject the signals from measurement electrodesthat have noise levels that exceed the noise threshold. In someexamples, signals from the measurements electrodes associated with noiselevels that exceed the noise threshold can be included, but the signalscan be scaled down (e.g., be associated with a lower weighting factor).

In some examples, the input from high-noise measurement electrodes canbe completely eliminated or rejected, as depicted in FIG. 5A. Method 500may comprise contacting a reference electrode to a first skin region instep 502, and contacting one or more of a plurality of measurementelectrodes to a second skin region in step 504. For instances where thereference electrode can be located on a wrist-worn device such as awatch, method 500 may comprise putting on the watch such that thereference electrode can contact the skin region at or near the wrist,and the measurement electrode(s) can contact a second region of skin(e.g., a fingertip). For example, if the measurement electrode(s) arelocated on the watch, the user may touch the tip of his/her finger tothe surface of the watch that has the measurement electrode(s).

In some examples, if the measurement electrode(s) are located on aseparate accessory device, the user may contact the measurementelectrode(s) by contacting the accessory device. After the referenceelectrode and the measurement electrode(s) have contacted the skin ofthe user, method 500 may comprise measuring the noise levels for eachmeasurement electrode in step 506. For example, the impedance and/orelectrical signals may be measured for each measurement electrode(s).Such measurements can be transmitted from the measurement electrode(s)to the interface module and then transmitted to the controller, usingwired and/or unwired communications.

In some examples, the controller can optionally average the noise levelsfrom each of the measurement electrode(s) in step 508. The average noiselevel can be used to determine a noise threshold against which the noiselevels of each of the measurement electrodes can be compared.Alternatively, the noise threshold may be preselected or predetermined,and may be independent of the average measured noise level of themeasurement electrodes. Alternatively, in some examples, a preselectedor predetermined noise threshold may be adjusted based on the noiselevels of the measurement electrodes (e.g., shifted upwards or downwardsbased on the computed average noise level). Once a noise threshold hasbeen determined and/or calculated, the controller may identify themeasurement electrodes with noise levels that are at or below thethreshold noise levels (which may be referred to as “low-noise”measurement electrodes) in step 510. The controller may send a commandsignal to the interface module with instructions to acquire and transmitsignals only from low-noise measurement electrode(s). Signals fromhigh-noise measurement electrode(s) (i.e., any measurement electrodesthat are not low-noise measurement electrodes) may be rejected by theinterface module.

In some examples, the controller may send a command signal to theinterface module to acquire and transmit signals from the measurementelectrode(s) with the least amount of noise. For example, the controllermay rank the measurement electrodes based on their relative noise levelsand issue commands to the interface module to gather and transmitsignals only from some (e.g., three, four, five, etc.), but not all,measurement electrodes with the least noise. After sufficient ECG datahas been acquired by the controller (e.g., after a period of time, suchas about 5-20 seconds), the controller may generate an ECG waveformbased on the signals from the low-noise measurement electrodes in step514. Optionally, the generated ECG waveform may be displayed to the useror practitioner and/or transmitted to a remote server for storage and/orfurther analysis.

In some examples, spatial filtering can include scaling down the signalsassociated with or under-sampling high-noise measurement electrode(s),as depicted in FIG. 5B. Method 520 may comprise contacting a referenceelectrode to a first skin region in step 522, and contacting a pluralityof measurement electrodes to a second skin region in step 524. Forexamples where the reference electrode can be located on a wrist-worndevice such as a watch, method 520 may comprise putting on the watchsuch that the reference electrode can contact the skin region at or nearthe wrist, and the plurality of measurement electrodes can contact asecond region of skin (e.g., a fingertip). For example, if the pluralityof measurement electrodes is located on the watch, the user may touchthe tip of his/her finger to the surface of the watch that has theplurality of measurement electrodes.

In some examples, if the plurality of measurement electrodes is locatedon a separate accessory device, the user may contact the plurality ofmeasurement electrodes by contacting the accessory device. After thereference electrode and the plurality of measurement electrodes contactto the skin of the user, method 520 may comprise measuring the noiselevels for each measurement electrode in step 526. For example, theimpedance and/or electrical signals may be measured for each measurementelectrode. Such measurements can be transmitted from the measurementelectrode(s) to the interface module and then transmitted to thecontroller, using wired and/or unwired communications.

In some examples, the controller can optionally average the noise levelsfrom each of the measurement electrodes in step 528. The average noiselevel may be used as a noise threshold against which the noise levels ofeach of the measurement electrodes may be compared. Alternatively, thenoise threshold may be preselected or predetermined and may beindependent of the average measured noise level of the measurementelectrodes. Alternatively, a preselected or predetermined noisethreshold may be adjusted (e.g., shifted upwards or downwards based onthe computed average noise level) based on the noise levels of themeasurement electrodes. Once a noise threshold has been determinedand/or calculated, the controller may identify the measurementelectrode(s) (e.g., “low-noise” measurement electrodes) with noiselevels that are at or below the noise threshold in step 530. Thecontroller may also identify the electrodes (e.g., “high-noise”measurement electrodes) with noise levels that are above the noisethreshold levels in step 532.

In some examples, the controller can send a command signal to theinterface module with instructions to adjust the sampling frequency forlow-noise and high-noise measurement electrodes in step 534. Forexample, the interface module can adjust the switching in themultiplexer(s) such that signals from low-noise measurement electrodescan be transmitted to the controller more frequently than signals fromhigh-noise measurement electrodes. The sampling frequency of aparticular measurement electrode can be inversely related (e.g.,inversely proportional, etc.) to its noise level. For example, the noiselevels of the plurality of measurement electrodes can be ranked by thecontroller; the frequency at which the multiplexer can switch to aparticular measurement electrode and can transmit its signal to thecontroller can be inversely proportional to the ranking of thatparticular measurement electrode.

In some variations, the interface module can be configured to (e.g.,using a plurality of staged multiplexers) provide a dedicated channelbetween low-noise measurements electrodes to the controller and thenmultiplex between the high-noise measurement electrodes. In someexamples, the controller can prioritize the transmission of ECG datafrom low-noise measurement electrodes over high-noise measurementelectrodes by increasing the multiplexer selection frequency and/orsampling frequency of the low-noise measurement electrodes. In someexamples, the controller can reduce the selection frequency and/orsampling frequency of the high-noise measurement electrodes. In someinstances, the controller can generate a good quality, low-noise ECGwaveform, without increasing the power consumption or bandwidthrequirements of the device.

Alternatively or additionally to adjusting the characteristics of dataacquisition, the signal(s) from high-noise measurement electrode(s) canbe processed differently by the controller as compared to the signalsfrom the low-noise measurement electrode(s). For example, to the extentthat the overall ECG waveform can be a weighted sum of the signals fromthe plurality of measurement electrodes, the controller may scale downthe magnitude or weight of the signal from high-noise measurementelectrodes when computing the overall ECG waveform. After sufficient ECGdata has been acquired by the controller (e.g., after a period of time,such as about 5-20 seconds), the controller can generate an ECG waveformbased on the signals from the low-noise measurement electrodes in step522. Optionally, the generated ECG waveform may be displayed to the useror practitioner and/or transmitted to a remote server for storage and/orfurther analysis.

The variations of spatial filtering methods described above and depictedin FIGS. 5A-5B can classify the noise characteristics of the measurementelectrodes before ECG data and/or signals are acquired and processed. Insome examples, the noise characteristics of the measurement electrodescan be evaluated before, during, and/or after data acquisition. Forexample, in some instances where the user can move during dataacquisition, a measurement electrode that was previously determined tohave subthreshold noise levels may be affected by motion artifacts,acquiring signals with unfavorable noise characteristics. In suchscenario, it may also be that a measurement electrode previouslydetermined to have suprathreshold noise levels may have improved noiseconditions, for example, due to better skin contact or being moved to alocation with fewer sweat glands, etc. A controller that can evaluatesthe noise characteristics of the measurement electrodes throughout dataacquisition interval may detect this change and may dynamically adjustthe sampling frequency and/or grouping of the measurement electrodes,whose noise characteristics may have changed.

In some examples, where the overall ECG waveform can be a weighted sumof the signals from the measurement electrodes, the weighting factor mayvary as a function of time such that when the signal levels from aparticular measurement electrode exceed the noise threshold, theweighting factor can be dynamically changed (e.g., decrease for thattime period). In some examples, when the signal levels from that samemeasurement electrode are below the noise threshold, the weightingfactor can be dynamically changed (e.g., increased for that timeperiod). The noise characteristics of the measurement electrodes may beperformed on a sample-by-sample basis or at set time intervals duringthe ECG data acquisition period (e.g., for an acquisition period of 10seconds, the noise characteristics of the measurement electrodes may bere-evaluated every second, or every two seconds, or every 0.5 seconds,etc.).

The controller can be configured to generate notifications to the userand/or medical practitioner regarding the signal quality and/or noiselevels of the signals from the measurement electrodes. For example, ifat any point the majority of the measurement electrodes havesuprathreshold noise levels, and/or exceed a maximum acceptable noisethreshold (i.e., such that an interpretable ECG waveform cannot begenerated (e.g., the data is too sparse or the SNR is below a certainthreshold)), the controller can prompt the user to re-position orotherwise adjust one or more measurement electrode(s). For example, thecontroller may suggest that the user position one or more measurementelectrode(s) at a flatter anatomical region, and/or press one or moremeasurement electrode(s) to more intimately contact the skin surface,etc. In some examples, the controller can indicate exactly whichmeasurement electrode(s) have unusual levels of noise, and the user mayinspect those measurement electrode(s) and check their contact with theskin region. In some examples, the controller may also generate an ECGwaveform form that may be projected to the user on a display of themobile or wearable device, and/or transmitted to a remote server forstorage and/or further analysis.

Although descriptions given herein have been in relation to certainexamples, various additional examples and alterations to the describedexamples are contemplated within the scope of the disclosure. Thus, nopart of the foregoing description should be interpreted to limit thescope of the disclosure as set forth in the following claims. For all ofthe examples described above, the steps of the methods need not beperformed sequentially. The foregoing description, for purpose ofexplanation, has been described with reference to specific examples.However, the illustrative discussions above are not intended to beexhaustive or to limit the disclosure to the precise forms disclosed.Many modifications and variations are possible in view of the aboveteachings. The examples were chosen and described in order to bestexplain the principles of the techniques and their practicalapplications. Others skilled in the art are thereby enabled to bestutilize the techniques and various examples with various modificationsas are suited to the particular use contemplated.

Although the disclosure and examples have been fully described withreference to the accompanying drawings, it is to be noted that variouschanges and modifications will become apparent to those skilled in theart. Such changes and modifications are to be understood as beingincluded within the scope of the disclosure and examples as defined bythe claims.

As described above, one aspect of the present technology is thegathering and use of data available from various sources to improve thedelivery to users of invitational content or any other content that maybe of interest to them. The present disclosure contemplates that in someinstances, this gathered data may include personal information data thatuniquely identifies or can be used to contact or locate a specificperson. Such personal information data can include demographic data,location-based data, telephone numbers, email addresses, home addresses,or any other identifying information.

The present disclosure recognizes that the use of such personalinformation data, in the present technology, can be used to the benefitof users. For example, the personal information data can be used todeliver targeted content that is of greater interest to the user.Accordingly, use of such personal information data enables calculatedcontrol of the delivered content. Further, other uses for personalinformation data that benefit the user are also contemplated by thepresent disclosure.

The present disclosure further contemplates that the entitiesresponsible for the collection, analysis, disclosure, transfer, storage,or other use of such personal information data will comply withwell-established privacy policies and/or privacy practices. Inparticular, such entities should implement and consistently use privacypolicies and practices that are generally recognized as meeting orexceeding industry or governmental requirements for maintaining personalinformation data private and secure. For example, personal informationfrom users should be collected for legitimate and reasonable uses of theentity and not shared or sold outside of those legitimate uses. Further,such collection should occur only after receiving the informed consentof the users. Additionally, such entities would take any needed stepsfor safeguarding and securing access to such personal information dataand ensuring that others with access to the personal information dataadhere to their privacy policies and procedures. Further, such entitiescan subject themselves to evaluation by third parties to certify theiradherence to widely accepted privacy policies and practices.

Despite the foregoing, the present disclosure also contemplates examplesin which users selectively block the use of, or access to, personalinformation data. The present disclosure contemplates that hardwareand/or software elements can be provided to prevent or block access tosuch personal information data. For example, in the case ofadvertisement delivery services, the present technology can beconfigured to allow users to select to “opt in” or “opt out” ofparticipation in the collection of personal information data duringregistration for services. In another example, users can select not toprovide location information for targeted content delivery services. Inyet another example, users can select to not provide precise locationinformation, but permit the transfer of location zone information.

Therefore, although the present disclosure broadly describes use ofpersonal information data to implement one or more various disclosedexamples, the present disclosure also contemplates that the variousexamples can also be implemented without the need for accessing suchpersonal information data. That is, the various examples of the presenttechnology are not rendered inoperable due to the lack of all or aportion of such personal information data. For example, content can beselected and delivered to users by inferring preferences based onnon-personal information data or a bare minimum amount of personalinformation, such as the content being requested by the deviceassociated with a user, other non-personal information available to thecontent delivery services, or publically available information.

A device is disclosed. The device can comprise: one or more measurementelectrodes configured to contact one or more first areas of a skinsurface, each measurement electrode being independently measurable andconfigured to generate a measurement signal indicative of one or moreelectrical signals of a user, the measurement signal included in aplurality of measurement signals; and a controller configured to:receive the plurality of measurement signals, compare each measurementsignal to a noise threshold, reject or apply a first weighting factor toeach measurement signal having a level greater than or equal to thenoise threshold, perform one or more of accepting and applying a secondweighting factor to each measurement signal having a level less than thenoise threshold, and determine one or more physiological parameters fromthe accepted measurement signals. Additionally or alternatively, in someexamples, some of the one or more measurement electrodes are configuredto contact an area of the skin surface different from other measurementelectrodes. Additionally or alternatively, in some examples, the devicefurther comprises: a reference electrode configured to contact a secondarea of the skin surface and located on a lower surface of a housing ofthe device, wherein the one or more measurement electrodes are locatedon an upper surface, opposite the lower surface, of the housing.Additionally or alternatively, in some examples, some of the one or moremeasurement electrodes are located at a first location of the device andothers of the one or more measurement electrodes are located at a secondlocation, separate and distinct from the first location, of the device.Additionally or alternatively, in some examples, the one or more firstareas of the skin surface are located proximate to each other.Additionally or alternatively, in some examples, the device furthercomprises: one or more communications channels, each communicationchannel associated with one of the one or more measurement electrodes.Additionally or alternatively, in some examples, the one or moremeasurement electrodes include one or more first measurement electrodesand one or more second measurement electrodes, the one or more firstmeasurement electrodes associated with a level of noise lower than theone or more second measurement electrodes, the device furthercomprising: one or more communications channels, each communicationchannel associated with one of the one or more first measurementelectrodes; and one or more multiplexers configured to dynamicallyreconfigure connections of the one or more second measurement electrodesto the controller.

A method is disclosed. The method can comprise: contacting one or morefirst areas of a skin surface of a user with one or more measurementelectrodes; for each measurement electrode, measuring one or moreelectrical signals of the user and generating one or more measurementsignals indicative of the measured one or more electrical signals;transmitting the one or more measurement signals using one of one ormore communications channels to a controller; and determining one ormore physiological parameters from the transmitted one or moremeasurement signals. Additionally or alternatively, in some examples,the method further comprises: for each measurement electrode, comparingthe one or more measurement signals to a noise threshold level; anddetermining one or more first measurement electrodes from the one ormore measurement electrodes and one or more second measurementelectrodes from the one or more measurement electrodes based on thecomparison, the one or more first electrodes having measurement signalsless than the noise threshold level and the one or more secondelectrodes having measurement signals greater than or equal to the noisethreshold level or a standard deviation from the noise threshold level,wherein determining the one or more physiological parameters includemeasurement signals associated with the one or more first electrodes.Additionally or alternatively, in some examples, the determining the oneor more physiological parameters excludes measurement signals associatedwith the one or more second electrodes. Additionally or alternatively,in some examples, the method further comprises: applying one or morefirst weighting factors to the measurement signals associated with theone or more first measurement electrodes; and applying one or moresecond weighting factors, less than the first weighting factor, to themeasurement signals associated with the one or more second measurementelectrodes. Additionally or alternatively, in some examples, each firstweighting factor is inversely proportional to a noise level of theassociated first measurement electrode, and each second weighting isinversely proportional to a noise level of the associated secondmeasurement electrode. Additionally or alternatively, in some examples,after measuring the one or more electrical signals using eachmeasurement electrode, for each first measurement electrode, measuringone or more electrical signals of the user and generating one or moresecond measurement signals indicative of the measured one or moreelectrical signals. Additionally or alternatively, in some examples,measuring the one or more electrical signals for each first measurementelectrode includes a first measurement frequency, and measuring the oneor more electrical signals for each second measurement electrodeincludes a second measurement frequency, the first measurement frequencygreater than the second measurement frequency. Additionally oralternatively, in some examples, measuring the one or more electricalsignals for each measurement electrode includes a frequency inverselyproportional to a noise level associated with the measurement electrode.Additionally or alternatively, in some examples, the method furthercomprises: for each measurement electrode, measuring one or more secondelectrical signals of the user; generating one or more secondmeasurement signals indicative of the measured one or more secondelectrical signals; comparing the one or more second measurement signalsto the noise threshold level; determining a change in noise level basedon the comparison; and reassigning the one or more measurementelectrodes associated with the change in noise level. Additionally oralternatively, in some examples, the one or more first areas of the skinsurface include a thumb and an index finger of the user, wherein themeasuring the one or more electrical signals is after the thumb andindex finger contact the one or more measurement electrodes.Additionally or alternatively, in some examples, the measuring the oneor more electrical signals is simultaneous for all measurementelectrodes, and the transmitting the one or more measurement signals issimultaneous. Additionally or alternatively, in some examples, themethod further comprises: ordering noise levels associated with the oneor more measurement electrodes; and determining one or more firstmeasurement electrodes having a lower order than other measurementelectrodes, wherein the determining the one or more physiologicalparameters include measurement signals associated with the one or morefirst measurement electrodes. Additionally or alternatively, in someexamples, the method further comprises: comparing one or moremeasurement signals to a noise threshold level; and prompting the userto move at least one of the one or more measurement electrodes to adifferent area of the skin surface.

1. A device comprising: one or more measurement electrodes configured tocontact one or more first areas of a skin surface, each measurementelectrode being independently measurable and configured to generate ameasurement signal indicative of one or more electrical signals of auser, the measurement signal included in a plurality of measurementsignals; and a controller configured to: receive the plurality ofmeasurement signals, compare each measurement signal to a noisethreshold, reject or apply a first weighting factor to each measurementsignal having a level greater than or equal to the noise threshold,perform one or more of accepting and applying a second weighting factorto each measurement signal having a level less than the noise threshold,and determine one or more physiological parameters from the acceptedmeasurement signals.
 2. The device of claim 1, wherein some of the oneor more measurement electrodes are configured to contact an area of theskin surface different from other measurement electrodes.
 3. The deviceof claim 1, further comprising: a reference electrode configured tocontact a second area of the skin surface and located on a lower surfaceof a housing of the device, wherein the one or more measurementelectrodes are located on an upper surface, opposite the lower surface,of the housing.
 4. The device of claim 1, wherein some of the one ormore measurement electrodes are located at a first location of thedevice and others of the one or more measurement electrodes are locatedat a second location, separate and distinct from the first location, ofthe device.
 5. The device of claim 1, wherein the one or more firstareas of the skin surface are located proximate to each other.
 6. Thedevice of claim 1, further comprising: one or more communicationschannels, each communication channel associated with one of the one ormore measurement electrodes.
 7. The device of claim 1, wherein the oneor more measurement electrodes include one or more first measurementelectrodes and one or more second measurement electrodes, the one ormore first measurement electrodes associated with a level of noise lowerthan the one or more second measurement electrodes, the device furthercomprising: one or more communications channels, each communicationchannel associated with one of the one or more first measurementelectrodes; and one or more multiplexers configured to dynamicallyreconfigure connections of the one or more second measurement electrodesto the controller.
 8. A method comprising: contacting one or more firstareas of a skin surface of a user with one or more measurementelectrodes; for each measurement electrode, measuring one or moreelectrical signals of the user and generating one or more measurementsignals indicative of the measured one or more electrical signals;transmitting the one or more measurement signals using one of one ormore communications channels to a controller; and determining one ormore physiological parameters from the transmitted one or moremeasurement signals.
 9. The method of claim 8, further comprising: foreach measurement electrode, comparing the one or more measurementsignals to a noise threshold level; and determining one or more firstmeasurement electrodes from the one or more measurement electrodes andone or more second measurement electrodes from the one or moremeasurement electrodes based on the comparison, the one or more firstelectrodes having measurement signals less than the noise thresholdlevel and the one or more second electrodes having measurement signalsgreater than or equal to the noise threshold level or a standarddeviation from the noise threshold level, wherein determining the one ormore physiological parameters include measurement signals associatedwith the one or more first electrodes.
 10. The method of claim 9,wherein the determining the one or more physiological parametersexcludes measurement signals associated with the one or more secondelectrodes.
 11. The method of claim 9, further comprising: applying oneor more first weighting factors to the measurement signals associatedwith the one or more first measurement electrodes; and applying one ormore second weighting factors, less than the first weighting factor, tothe measurement signals associated with the one or more secondmeasurement electrodes.
 12. The method of claim 11, wherein each firstweighting factor is inversely proportional to a noise level of theassociated first measurement electrode, and each second weighting isinversely proportional to a noise level of the associated secondmeasurement electrode.
 13. The method of claim 9, wherein aftermeasuring the one or more electrical signals using each measurementelectrode, for each first measurement electrode, measuring one or moreelectrical signals of the user and generating one or more secondmeasurement signals indicative of the measured one or more electricalsignals.
 14. The method of claim 9, wherein measuring the one or moreelectrical signals for each first measurement electrode includes a firstmeasurement frequency, and measuring the one or more electrical signalsfor each second measurement electrode includes a second measurementfrequency, the first measurement frequency greater than the secondmeasurement frequency.
 15. The method of claim 8, wherein measuring theone or more electrical signals for each measurement electrode includes afrequency inversely proportional to a noise level associated with themeasurement electrode.
 16. The method of claim 8, further comprising:for each measurement electrode, measuring one or more second electricalsignals of the user; generating one or more second measurement signalsindicative of the measured one or more second electrical signals;comparing the one or more second measurement signals to the noisethreshold level; determining a change in noise level based on thecomparison; and reassigning the one or more measurement electrodesassociated with the change in noise level.
 17. The method of claim 8,wherein the one or more first areas of the skin surface include a thumband an index finger of the user, wherein the measuring the one or moreelectrical signals is after the thumb and index finger contact the oneor more measurement electrodes.
 18. The method of claim 8, wherein themeasuring the one or more electrical signals is simultaneous for allmeasurement electrodes, and the transmitting the one or more measurementsignals is simultaneous.
 19. The method of claim 8, further comprising:ordering noise levels associated with the one or more measurementelectrodes; and determining one or more first measurement electrodeshaving a lower order than other measurement electrodes, wherein thedetermining the one or more physiological parameters include measurementsignals associated with the one or more first measurement electrodes.20. The method of claim 8, further comprising: comparing one or moremeasurement signals to a noise threshold level; and prompting the userto move at least one of the one or more measurement electrodes to adifferent area of the skin surface.